1. Field of the Invention
The present invention relates to a recording material utilizing a novel coloring mechanism, having excellent background preservability with minimum coloring of the background.
2. Discussion of Background
Generally, recording materials comprise a support and a recording layer formed thereon, which comprises as main components a colorless or light colored electron-donating dye precursor, and an electron-accepting color developer. These dye precursor and color developer are caused to react instantly upon the application of recording energy thereto to produce recorded images, for instance, by thermosensitive recording method, pressure-sensitive recording method and non-impact electric recording method, and the like, as disclosed in Japanese Patent Publications 43-4160 and 45-14039.
Recording materials utilizing such an electron-donating dye precursor and an electron-accepting color developer have advantages over other recording materials that they have excellent characteristics such as good appearance, nice touch and being capable of producing images with high coloring density, but also have disadvantage that the image preservability thereof is poor. Specifically, when image areas come into contact with plastics such as polyvinyl chloride, images are decolorized by plasticizers and additives contained in such plastics, or when image areas come into contact with chemicals contained in foods or cosmetics, such image areas are easily decolorized, or the background thereof is easily colored.
In addition to the above recording materials, chelate according materials recording materials are known, which utilize metallic compounds. More specifically, Japanese Patent Publications 32-8787 and 34-6485 disclose chelate recording materials comprising an organic reducing agent, chelating agent, or a sulfur compound as an electron donator, and an organic acid metal salt as an electron acceptor as examples of such chelate recording materials.
However, in comparison with leuco recording materials, such chelate recording materials have excellent solvent resistance and plasticizer resistance, but have two significant drawbacks that the background thereof is colored when coming into contact with plasticizers, and the recording sensitivity thereof is low.
In order to prevent the coloring of the background, the above-mentioned Japanese Patent Publications propose recording materials comprising an organic metal salt in one layer, and an organic reducing agent, a chelate agent or a sulfur compound in another layer. According to this method, the problem of the coloring of the background can be solved, but the recording sensitivity is further decreased. Furthermore, the above-mentioned Japanese Patent Publications propose the use of a metal soap as a sensitizer, but the use of a metal soap causes background fogging and considerably reduces the preservability of the recording material.
Many proposals have been made in an attempt to solve these problems of the conventional recording materials, but those problems have not yet been solved completely.